The present invention relates to fluorescent pigment compositions and processes for the making thereof. The present invention also relates to articles formed from the fluorescent pigment compositions.
It is generally known that fluorescent pigments are often referred to as daylight fluorescent colors. The term pigment in this context is inaccurate since by definition a pigment is understood to mean a pure unextended inorganic or organic colorant that, unlike a dye, is insoluble in all types of solvents. However, most daylight fluorescent colors are not truly pigments but really solid solutions of fluorescent dyes in transparent synthetic resins that are finely ground to a particle size in the range of 2 to 5 microns. These pigments can alternatively be described as transparent plastic materials colored with fluorescent dyes. Polyamides may be used as carrier materials for these compositions. Unlike conventional organic pigments, which are usually precipitated single components, fluorescent pigments are solid state solutions of common fluorescent dyes in polymeric resins or matrices.
The daylight fluorescent colors belong to the dye families known as rhodamines, fluoresceins, coumarins, naphthalimides, benzoxanthenes and acridines. Typical dyes include Basic Red 1, Basic Violet 10, Basic Violet 11, Basic Violet 16, Basic Yellow 40, Solvent Yellow 44, Solvent Yellow 131 and Solvent Yellow 135. The fluorescent dyes comprise from about 0.1 to about 15% of the total weight of the pigment.
U.S. Pat. No. 4,153,618 and U.S. Pat. No. 4,299,959 disclose a fluorescent pigment consisting of N-substituted iminocoumarins.
U.S. Pat. No. 4,911,830 discloses low plate-out fluorescent pigment concentrates that are of the daylight fluorescent color type.
U.S. Pat. No. 4,975,220 discloses a fluorescent pigment composition comprising a fluorescent dye combined in a polyamide-polyester thermoplastic resin.
U.S. Pat. No. 5,094,777 discloses a fluorescent composition including a fluorescent dye and a resin carrier. The fluorescent dye is of the daylight fluorescent-type and belongs to the dye families known as rhodamines, fluoresceins, coumarins, naphthalimides, benzoxanthenes, and acridines.
U.S. Pat. No. 5,236,621 discloses a thermoplastic organic fluorescent pigment that unlike conventional organic pigments is a solid state solution of fluorescent dyes. The fluorescent pigment includes from 85 to 99 weight percent polymer matrix and from 1 to 15 weight percent fluorescent dye, the weight percent being based on the combined weight of the polymer matrix and dye.
U.S. Pat. No. 5,294,664 discloses an aqueous dispersion of a fluorescent pigment comprising a water insoluble polymer, fluorescent dye, emulsifiers, and water. The fluorescent pigment which is suitable for use as an ink in thin film printing has an average particle size of from about 0.01 to about 1 microns, and the fluorescent pigment which is suitable for use as either a pigment suspension or a dry fluorescent pigment has a particle size up to 10 microns.
U.S. Pat. No. 5,439,971 discloses a low plate-out fluorescent pigment of the daylight fluorescent-type. The low plate-out fluorescent pigment comprises a pigment comprising a polymer selected from the group consisting of polyesters, melamine-formaldehyde resins and triazine-formaldehyde resins and a fluorescent dye, and a copolymer of ethylene and carbon monoxide. The copolymer has a molecular weight of about 1,000 to about 100,000, the copolymer containing carbon monoxide residue in the amount of about 5 to 30% by weight and the copolymer being in sufficient amount to disperse the pigment.
U.S. Pat. No. 6,110,566 discloses a colored article having fluorescent properties comprising a substantially solventless polyvinyl chloride matrix, a thioxanthene fluorescent dye, and a secondary or tertiary hindered amine light stabilizer having a molecular weight less than about 1000 grams/mole.
Unlike the fluorescent pigment compositions known above, the fluorescent pigment compositions of the present invention comprise true pigments. Surprisingly, in the present invention when either Pigment Violet 19 or Pigment Yellow 192 is used in an effective amount in a polyamide, with or without the presence of other additives, the result is a bright fluorescent yellow polymeric pigment composition.
Pigment Yellow 192 (CAS Registry No. 56279-27-7; TSCA Inventory Name: 7H,11H-Benz[de]imidazo[4xe2x80x2,5xe2x80x2:5,6]benzimidazo[2,1-a]isoquinoline-7,11-dione, 10,12-dihydro-) is a polycyclic pigment having the following structure: 
Pigment Yellow 192 is not known to fluoresce in polyamides.
Pigment Violet 19 (CAS Registry No. 1047-16-1; TSCA Inventory Name: Quino[2,3-b]acridine-7,14-dione, 5,12-dihydro) is a quinacridone pigment having the following structure: 
Pigment Violet 19 is known to have a range of shades from red-violet to bluish red and is not known to fluoresce. Quinacridones are not typically recommended for use in polyamides. This is generally because of poor dispersion and also because of burn out in nylon. The term xe2x80x9cburn outxe2x80x9d refers to the situation in which the thermal stability of the colorant is compromised. For example, there may be coloration changes. Polyamide fibers are characterized by high tensile strength, modulus and abrasion resistance; however, polyamides require stabilization against thermo-oxidative and photodegradation for demanding use applications. Therefore, further improvement in the stabilization systems for these materials is presently desired in such end uses as engineering resins, films, coatings, adhesives, plastics, fibers, monofilaments and nonwovens. Polyamides are also suitable in relatively high temperature processing of injection moldings. The polyamide structure contains labile hydrogens and exerts reductive or basic properties which are problematic from the standpoint of colorants. For example, in polyamide, an organic dye may undergo a significant loss of shade upon thermal processing at the typical melt processing temperatures for polyamide. It would be desirable to lessen the tendency of polyamide to exert this influence on dyes without sacrificing the desired physical properties of polyamides. One aspect of the present invention is directed to additives which are dispersed within the polyamide polymer by melt-processing at high temperatures above the glass transition, as in extrudates or moldings. It was unexpected to achieve fluorescent yellow pigment compositions for use in applications such as polyamide fibers or molded articles that have the advantageous properties of the present invention.
Currently, industry relies upon expensive fluorescent pigments and optical brighteners that are more on the green or blue side of the visible spectrum. Yellow fluorescent pigments are extremely expensive, require ultraviolet protection, and are difficult to disperse. Thus, there is a need for fluorescent pigment compositions such as in the present invention that are cost effective and easy to disperse yet are fluorescent in the yellow region of the electromagnetic visible spectrum.
It is an object of the present invention to provide a fluorescent yellow pigment composition comprising an effective amount of Pigment Violet 19 and a polyamide. The fluorescent composition may be in the form of an article, such as a molded, cast, or extruded article. It is another object of the present invention to provide a fluorescent yellow pigment composition comprising an effective amount of Pigment Yellow 192 and a polyamide. The fluorescent composition may be in the form of an article, such as a molded, cast, or extruded article. It is yet another object of the present invention to provide a fluorescent yellow pigment composition comprising a compound of the formula 
with enhanced fluorescence.
It is another object of the present invention to provide processes for making fluorescent yellow pigment compositions. In one embodiment of the present invention, the pigment is added to a carrier material to form a single pigment concentrate or masterbatch. The single pigment concentrate or masterbatch can also be enhanced by the addition of a compound of the formula 
Other additives may also be present in the single pigment concentrate or masterbatch.
It is yet another object of the present invention to provide a fluorescent article.